GE Multilin 489

5–46 489 GENERATOR MANAGEMENT RELAY – INSTRUCTION MANUAL
CHAPTER 5: SETPOINTS
The Volts Per Hertz elements may be used generator and unit transformer protection. They
are active as soon as the magnitude and frequency of V
ab
is measurable. The alarm
element is definite time; the trip element can be definite time or a curve. Once the V/Hz
measurement V
ab
exceeds the pickup level for the specified time, a trip or alarm will occur.
The reset rate is a linear reset time from the threshold of trip and should be set to match
cooling characteristics of the protected equipment. The measurement of V/Hz will be
accurate through a frequency range of 5 to 90 Hz. Settings less than 1.00 only apply for
special generators such as short circuit testing machines.
The formula for Volts/Hertz Curve 1 is:
(EQ 5.20)
where: T = trip time in seconds
D =
VOLTS/HERTZ TRIP DELAY setpoint
V = RMS measurement of Vab
F = frequency of Vab
V
NOM
= generator voltage setpoint
F
S
= generator frequency setpoint
Pickup =
VOLTS/HERTZ TRIP PICKUP setpoint
MESSAGE
VOLTS/HERTZ ALARM
PICKUP: 1.00 xNominal
Range: 0.50 to 1.99 ×Nominal in steps
of 0.01
MESSAGE
VOLTS/HERTZ ALARM
DELAY: 3.0 s
Range: 0.1 to 150.0 s in steps of 0.1
MESSAGE
VOLTS/HERTZ ALARM
EVENTS: Off
Range: On, Off
MESSAGE
VOLTS/HERTZ
TRIP: Off
Range: Off, Latched, Unlatched
MESSAGE
ASSIGN TRIP
RELAYS (1-4): 1---
Range: Any combination of Relays 1 to
4
MESSAGE
VOLTS/HERTZ TRIP
PICKUP: 1.00 xNominal
Range: 0.50 to 1.99 ×Nominal in steps
of 0.01
MESSAGE
VOLTS/HERTZ TRIP
DELAY: 1.0 s
Range: 0.1 to 150.0 s in steps of 0.1
MESSAGE
VOLTS/HERTZ CURVE
RESET RATE: 1.4 s
Range: 0.0 to 999.9 s in steps of 0.1
MESSAGE
VOLTS/HERTZ TRIP
ELEMENT: Curve #1
Range: Curve #1, Curve #2, Curve #3,
Definite Time
T
D
VF⁄
V
nom
F
s
⁄()Pickup×
--------------------------------------------------
⎝⎠
⎛⎞
2
1–
-------------------------------------------------------------------= , when
V
F
---
Pickup>
Courtesy of NationalSwitchgear.com